Reliably monitoring exhaust gas constituents related to aftertreatment systems for internal combustion engines presents several challenges. Frequently, exhaust environments operate at very high temperatures that preclude use of many standard sensor types. Further, engine combustion constituents typically include soot and unburned hydrocarbons that can hamper operation of various sensing technologies. Present sensing technologies cannot detect various constituents of the exhaust gas and survive the exhaust environment. Various aftertreatment systems and technologies for internal combustion engines experience wear, failure, and operational variability that affect the final emissions of the engine-aftertreatment system. Presently available sensing technologies have very limited feedback for aftertreatment systems, making control and diagnostics for aftertreatment systems difficult. Thus, there is an ongoing demand for further contributions in this area.